Is volcanic activity on the rise – and if so, where's next?

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In November Mount Agung on Bali erupted, sending plumes of smoke and ash 30,000 feet into the air and shutting the popular holiday island’s only airport. More than 400 flights a day were cancelled until Denpasar reopened.

Last month eyes turned to Hawaii, where Kilauea, said to be continuously simmering, blew violently, spewing out lava flows, cracking the earth and spitting out rock projectiles. The volcano remains on high alert.

Three days of national mourning have been declared after the volcano hurled rocks, smoke and ash into the sky. El Rodeo, a village nearby, has been all-but destroyed by a flow of lava.

Fuego erupted on Sunday in GuatemalaCredit:
Getty

Are volcanoes getting more active?

According to the National Museum of Natural History’s Global Volcanism Program, more than 1,500 volcanoes on the planet have erupted at some point in the last 11,500 years, the current geological epoch otherwise known as the Holocene period.

Today, some 15 are erupting, a figure common for any given point in modern history.

Clive Oppenheimer, professor of volcanology at the University of Cambridge, says there has not been an increase in volcanic activity.

“There have been quite a few eruptions in the news lately, so people question whether there’s an increase in rates of volcanism that we’re seeing just now, and this isn’t really the case,” he said.

“Eruptions are happening all the time - some make the news headlines and others don’t.

The ongoing eruption on Kilauea in Hawaii as captivated audiences around the worldCredit:
REUTERS/TERRAY SYLVESTER

“If we look at the statistics back in time, the main thing we see is a reporting bias. There are not many eruptions during World War Two, for example, when people had other things to really worry about.

“So of course things will flare up in one place or another place and then it will be very much how those eruptions affect people and where abouts in the world [as to] whether that then becomes newsworthy.”

“In Hawaii, in Indonesia, in Italy, where there are volcanoes known to erupt, there are agencies, institutes, observatories, that are doing 24/7 monitoring, measuring the earthquakes occurring on volcanoes, looking at the changing shapes of the volcano and looking at the gas emissions, so it’s possible to make some sort of assessment of what the volcano might be gearing up to in the future,” he said.

“Of course, [the next big eruption] is likely to be in the a volcanic region that we already know about. But I think one of the lessons of history, even recent history, is the really big eruptions have not happened at volcanoes that scientists were looking at.

“We tend to focus on volcanoes that have erupted in recent times but the really big events can happen at volcanoes that have been quiet, that have been dormant for many centuries or even millennia. They’ve been biding their time, building up a reservoir of magma in the crust.”

He cited the eruptions of Mount Pinatubo in the Philippines in 1991, El Chichon in Mexico in 1982 and Chaiten in Chile in 2008 as volcanoes that were not on the scientific radar yet produced very large eruptions.

“That’s something we should keep in mind going forward,” he said. “It might not be a volcano that’s currently well monitored that will lead to the next major volcanic eruption.”

Oppenheimer says the pressure on scientists to monitor and predict the behaviour of volcanoes is equal to that of communicating the threat to the public.

“This where the really important work is needed,” he said. “The science can be fantastic. We never have certainty in predicting volcanic eruptions but we might have some reasonable evidence.

“If you can’t communicate that to the population at risk, to the civil protection authorities that need to start an evacuation, then all the science is useless.”

Will climate change lead to more volcanic eruptions?

A 2017 study published in the Geology journal researched a link between melting glaciers and ice caps and an increase in volcanic activity. Looking at a period of cooling about 5,500 years ago in Iceland, the researchers found that growing ice coverage coincided with a decrease in eruptions. The same was true in reverse: when the ice retreated, the number of eruptions increased.

As the world’s ice sheets shrink and glaciers melt, it has been suggested the retreat could usher in a new era of volcanic activity.

Oppenheimer explained the link between ice ages and rates of volcanism.

“We do see effects with deglaciation of the last ice age with the relatively sudden unloading of volcanic regions that might have been under two to three kilometres of ice,” he said. “When that is moved that can cause melting that fuels volcanoes, it can trigger eruptions, and that leads us to the question well then what about the future, as we are seeing global warming and more deglaciation.

“But it’s something one could only really study from the point of view of models perhaps, but also from statistics so you’d really want lots and lots of data.

“I think we can kind of do that when we look back at the end of the last ice age, but as we’re going forward in the next century, I don’t think we will see any kind of statistical blip related to anthropogenic climate change today.”

Mount Agung, Bali, smokes in the backgroundCredit:
Getty

Why are volcanoes dangerous?

Given that some volcanoes are constantly simmering, or that many eruptions go unnoticed every year, it might be difficult to put a finger on exactly how many volcanoes are dangerous.

In Hawaii, the lava flows mainly drained into the sea, while the volcano spat some projectiles across the nearby surroundings. In Guatemala, lava flows seemed to have caused destruction. But there are many ways volcanoes can impact a country, region, or indeed, the world.

Oppenheimer cites mud flows and pyroclastic flows - “hot ash, and rock and pumis [that] has been blasted up into the atmosphere [and] collapses back to the ground and flows as a kind of hurricane-like current down the flanks of the the volcano” - as two of the more destructive results of an eruption.

But he also cites the impact on vegetation and livestock from gas emissions. In 1815, after the eruption of Tambora in Indonesia, one of the most powerful eruptions in recorded history, there followed in 1816 the Year Without a Summer after ash from the eruption spread around the world lowering global temperatures, sparking extreme weather and causing harvest failures.

“In the future, we can’t rule out a very great eruption of that scale,” he said. “The same sulphur release as Tambora in 1815 might [today] also have repercussions on global food security.”

Where are all the world’s volcanoes?

The majority are found in clusters, or strips, mostly following the faultlines of the world’s tectonic plates. For this reason, mapping the world’s volcanoes according to country is slightly misleading, as most are linked to the same geological highway.

The "Ring of Fire" that encircles the Pacific Ocean – which stretches up the west coast of the Americas, around and across to Asia, looping down to the east of Japan, before overwhelming much of Indonesia and the Philippines and whipping around Australasia – boasts the most, with 452.

This is why Indonesia has the third most volcanoes in the world, at 139. The island of Bali has three: Agung, Batur and Buyan-Bratan. Japan comes fourth with 112. Chile (also on the Ring of Fire, on the cusp of the South American plate) is fifth, with 104.

But it is the United States that takes the title with the most, 173, followed by Russia, with 166 – both large countries, and also both on the Ring of Fire.

The 10 countries with the most volcanoes

United States - 173

Russia - 166

Indonesia - 139

Japan - 112

Chile - 104

Ethiopia - 57

Papua New Guinea - 53

Philippines - 50

Mexico - 43

Argentina - 39

Another hotspot for volcanoes is on the African continent, where the African Plate meets the Arabian Plate, which is why Kenya (23), Tanzania (10) and Ethiopia (57) boast a wealth of volcanoes.